change default oom victim container name

[gaorong]

background

In kubernetes, kubelet subscribes to cadvisor and follow the OOM event, the request is as below,

	request := events.Request{
		EventType: map[cadvisorapi.EventType]bool{
			cadvisorapi.EventOom: true,
		},
		ContainerName:        "/",
		IncludeSubcontainers: false,
	}

kubelet's related code is here, then cadvisor will return all system oom event against this request.

what happened to me

However, when I used this request as kubernetes with the only difference is the eventType, which is EventOomKill in mine, it seems not to work to me, I expect that cadvisor return all system oom kill event. (aside: The difference of EventOomKill and EventOom is described here).

cadvisor's behavior

When some process indeed been killed because of oom, cadvisor check if event satisfies request. In a situation described as above, cadvisor checks satisfaction and invokes checkIfIsSubcontainer, but checkIfIsSubcontainer always fails, which shouldn't happen.

this PR fixes this bug by initializing OomInstance.VictimContainerName as '/', which is the same as what OomInstance.ContainerName does. when oom parser parses kmsg's log and doesn't find a killed container, it will stay this name. and then if someone request as above, it will match this oom kill event and return this event.

[k8s-ci-robot]

Hi @gaorong. Thanks for your PR.

I'm waiting for a google or kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[gaorong]

/assign @vmarmol

[dashpole]

/ok-to-test

[gaorong]

the CI is green now

[dashpole]

/lgtm

[dashpole]

lgtm